The present invention relates to a powder molding pressing machine and, more particularly, to a method and apparatus for connecting a plurality of punches to a main body of the pressing machine.
In a tool-set type pressing machine having a plurality of punches for forming, for example, a double or triple punch pressing machine, it is necessary to operate each of the punches separately and independently from the other punches, and accordingly, such a pressing machine comprises, as shown in FIG. 5, a punch operating device 101 including a hydraulic cylinder or an air cylinder, and an auxiliary device, in addition to a pressurizing device 100 provided in the main body of the pressing machine.
In a conventional pressing machine, the punch operating device 101 and, further, an upper punch unit 103 including a plurality of punches are assembled into a tool set 102.
Punches and other components are assembled as follows. A third lower punch 107, a second lower punch 106, a first lower punch 105 and then a die 108 are sequentially connected vertically in this order below a core 104, and the core 104 and the die 108 are then raised to connect a third upper punch 111 to the tool set 102 while it is axially aligned with the core 104. After a second punch 110 is connected, a first punch 109 is connected while it is being positioned relative to the die 108.
However, in the conventional tool-set type pressing machine, each of the first, second and third upper punches 109, 110 and 111 of the upper punch unit 103 must be fastened by a bolt inserted from below, thus reducing the assembling efficiency.
Furthermore, if only the third upper punch 111, provided substantially at the center of the tool set 102, needs to be replaced, the first and second upper punches 109, 110 must also be detached, in other words, the whole upper unit 103 must be disassembled and then assembled again after such replacement, thus considerably degrading the working efficiency in replacement or maintenance.
It is normal practice for such a tool-set type pressing machine that punches are assembled into a tool set separately from the main body of the machine. More specifically, a plurality of tool sets having punches of various shapes and sizes are prepared beforehand, and a tool set suitable for a desired product is selectively attached to the main body of the pressing machine. Because a plurality of tool sets are needed for this normal practice, the production cost is thereby inevitably raised.
Particularly, a tool set having a plurality of punches needs rather sophisticated and therefore expensive operating and auxiliary devices for the punches, thus further pushing up the production cost.
Furthermore, it is necessary for the punch operating device and the auxiliary device to arrange an air or hydraulic piping system, so that the pipes must be connected every time a tool set is replaced, thus making such tool-set replacement troublesome and time-consuming.
In addition, since a large-size pressing machine requires a hydraulic system and, therefore, is provided with wide pipes, the tool-set replacement is even more difficult in such a large machine. Further, the piping system may be contaminated with undesired substances during replacement.